The invention relates to a device for removing excess sprayed material during application by spraying of wet lacquer according to the preamble of patent claim 1.
Such devices are described in the DE-AS 26 20 673 and DE-OS 36 19 674. In the known devices excess sprayed material is removed first along the partition by a film of water flowing down over the partition, carrying along sprayed particles to be removed, and fed to a water bath present at the bottom end of the suction booth. Thus, air freed almost completely of sprayed particles flows through the openings in the partition. In addition, there is an air flow directed closely over the surface of the water bath and located behind the partition, thus producing further removal of the sprayed particles.
The method of removing excess sprayed material of wet lacquer in which the sprayed particles are collected by water, causes significant environmental problems, since the sprayed particles must be removed from the water before it can be guided into local sewers.
The invention is based on the problem of accomplishing the removal of excess sprayed material of wet lacquer without the assistance of water in such a manner that the removed sprayed particles can be directly dumped and optionally recycled. The problem is solved by the invention with the features of the invention.
Since the nozzles in the partition taper in the direction of flow, the result is first of all an air flow of high velocity, due to which the sprayed particles are led past the nozzle walls so fast that they have a negligible tendency to settle on the partition or the nozzle walls. Thus these parts of the device remain largely free of excess sprayed material. In the suction booth it is provided with its cross section and its smooth booth walls that an upwardly directed air flow is produced by which the sprayed particles are carried for such a long period of time that they dry and thus assume a dust-like nature. This is achieved in that the upwardly directed air flow exhibits a higher speed than the sinking speed of the sprayed particles in stagnant air. The drying process of the sprayed particles extends with certainty also to those sprayed particles that enter into the suction booth through the uppermost nozzle area, since above this uppermost nozzle area for the sprayed particles owing to the corresponding length of the suction booth a dwell period persists in which the air flow still carries the sprayed particles for at least about 1 second, in which time the sprayed particles can certainly dry.
Preferably a cleanable filter, from which the filtered sprayed particles are thrown in known manner as filter cakes, e.g., by a compressed air jet directed against the air current, is installed in front of the aspirator. To collect sprayed particles cleaned thus, a collecting device is provided in the suction booth. The collected material can be disposed by said device, but it can also be fed again into the spraying process, to which end the sprayed particles must naturally be dissolved in a solvent.
For constructive reasons, the nozzles are designed preferably as slot nozzles extending over a significant portion of the partition. These slot nozzles can be arranged both vertically and horizontally or also in combination.